Techniques developed in this laboratory for the cryopreservation and in vitro cultivation of larval Onchocerca volvulus are being employed in a series of morphogenetic, physiologic, chemotherapeutic and immunologic investigations of this parasite. The major objectives of the proposed research are: 1) to collect, cryopreserve and cultivate microfilariae and developing larvae obtained from onchocerciasis infected patients and black flies in Guatemala; 2) to describe and compare further, the sequential processes of morphogenesis of microfilariae to third stage infective larvae as it occurs in vitro and in vivo; 3) to explore promising modifications of the original in vitro system in order to increase the yield of intermediate and third stage larvae; and to refine the system for use in continuing physiologic, immunologic and chemotherapeutic research on this parasite.